One HTTPS call sends an email from your verified domain. No SDK required.
In the dashboard, open API keys and create a key with the emails:send scope. Copy the axm_k_live_ secret once.
Call https://mail.axene.io/v1/emails/ with an Authorization: Bearer axm_k_live_... header and a JSON body (from, to, subject, html).
You get back an email id. Poll /v1/emails/{id} or wire a webhook to follow delivery.